1. Field of the Invention
The present invention relates to a phase sheet, a method for fabricating the same and a stereoscopic display device using the same. More particularly, the present invention relates to a phase sheet for stereoscopic display allowing for a liquid crystal display device to display a stereoscopic image, a method for fabricating the same and a stereoscopic display device using the same.
2. Description of the Related Art
A conventional stereoscopic display device alternately displays an image component to be viewed by the right eye (hereinafter, simply referred to as a xe2x80x9cright-eye image componentxe2x80x9d) and an image component to be viewed by the left eye (hereinafter, simply referred to as a xe2x80x9cleft-eye image componentxe2x80x9d) at a high speed. These displayed image components are viewed by the human eyes as a stereoscopic image through a pair of spectacles in which the right-eye lens and the left-eye lens are alternately shut at a high speed. The operations of the pair of spectacles and the image display device are controlled to be synchronous with each other such that, when the right-eye lens of the spectacles is shut, the left-eye image component is perceived and that, when the left-eye lens of the spectacles is shut, the right-eye image is perceived. However, such a pair of spectacles used for stereoscopic display requires a complicated structure for alternately shutting the right-eye and the left-eye lenses at a high speed. In addition, a complicated controller for synchronizing the image components imaged via the spectacles with the image displayed on the display device is also required.
In another exemplary stereoscopic display device, a first and a second polarizer, each having a predetermined display unit, are adjacently disposed, such that the polarization directions thereof cross each other at a right angle, and polarizing films are alternately arranged on the plane of each polarizer to form a uniform arrangement pattern having a symmetry.
For example, Japanese Laid-Open Publication No. 7-5325 discloses a stereoscopic display device allowing for stereoscopic display by providing polarizing films corresponding to respective arrangement patterns for each of a pair of substrates disposed in a liquid crystal panel so as to face each other and by using a pair of spectacles including polarizing films having transmission axes which cross each other at a right angle and respectively correspond to the right eye and the left eye.
In general, an alignment film of a liquid crystal display used for a stereoscopic display device aligns the orientations of a liquid crystal material with a uniaxial direction by conducting a rubbing treatment. However, in the case of providing polarizing films, patterned so as to have the transmission axis directions defined in the above-described manner, for such a liquid crystal display, the stereoscopic display device is required to take either one of the following arrangements (1) and (2).
(1) An arrangement in which a Normally White (NW) mode and a Normally Black (NB) mode are associated with the left eye and the right eye, respectively.
Specifically, as shown in FIG. 10, in such a stereoscopic display device 10, a pair of substrates 100a and 100b , having alignment films (not shown) which have been subjected to a rubbing treatment in a direction 45 degrees away from an arbitrary direction X and in a direction 135 degrees away from the direction X, respectively, are disposed such that the rubbing directions cross each other at a right angle. A polarizing film 101a is provided over the substrate 100a. In a region corresponding to a left-eye pixel (i.e., a region associated with the NW mode), a transmission axis 102a of the polarizing film 101a is oriented so as to be aligned with a rubbing axis 104a on the substrate 100a (i.e., in the direction 45 degrees away from the direction X). On the other hand, in a region corresponding to a right-eye pixel (i.e., a region associated with the NB mode), a transmission axis 102b of the polarizing film 101a is oriented so as to be orthogonal to the rubbing axis 104a on the substrate 100a (i.e., in the direction 135 degrees away from the direction X). Furthermore, another polarizing film 101b is provided so as to face the surface of the substrate 100b opposite to the surface thereof facing the substrate 100a. In both regions corresponding to a left-eye pixel and a right-eye pixel, transmission axes 103a and 103b of the polarizing film 101b are oriented so as to be aligned with a rubbing axis 104b of the substrate 100b (i.e., in the direction 135 degrees away from the direction X).
(2) An arrangement in which the rubbing axes of the alignment films disposed over the substrates are not aligned with the transmission axes of the polarizing films.
Specifically, as shown in FIG. 11, in such a stereoscopic display device 10, a pair of substrates 100a and 100b having alignment films (not shown) which have been subjected to a rubbing treatment in a direction 45 degrees away from an arbitrary direction X and in a direction 135 degrees away from the direction X, respectively, are disposed such that these rubbing directions cross each other at a right angle. A polarizing film 111a is provided over the substrate 100a. In a region corresponding to a left-eye pixel, a transmission axis 112a of the polarizing film 111a is oriented so as to be parallel to the direction X (i.e., in the direction 0 degree away from the direction X). On the other hand, in a region corresponding to a right-eye pixel, a transmission axis 112b of the polarizing film 111a is oriented so as to be orthogonal to the direction X (i.e., in the direction 90 degrees away from the direction X). Furthermore, another polarizing film 111b is provided so as to face the surface of the substrate 100b opposite to the surface thereof facing the substrate 100a. In a region corresponding to a left-eye pixel, a transmission axis 113a of the polarizing film 111b is oriented so as to be orthogonal to the direction X (i.e., in the direction 90 degrees away from the direction X). On the other hand, in a region corresponding to a right-eye pixel, a transmission axis 113b of the polarizing film 111b is oriented so as to be parallel to the direction X (i.e., in the direction 0 degree away from the direction X).
However, a stereoscopic display device having the arrangement (1) or (2) has the following problems. In a stereoscopic display device having the arrangement (1), a color tone shift is caused between a resulting right-eye image component and a resulting left-eye image component. On the other hand, in a stereoscopic display device having the arrangement (2), since the vibration direction of polarized light transmitted through a liquid crystal layer existing between the substrates 100a and 100b is not aligned with any of the directions of the transmission axes of the polarizing films, a considerable amount of light is lost when the light is transmitted through the polarizing films. Consequently, an image having a satisfactory contrast ratio cannot be obtained.
Furthermore, a method for displaying a stereoscopic image by using a lenticular plate 120 as shown in FIG. 12 is also known. In a stereoscopic display device utilizing such a method, image components viewed from different directions, e.g., a right-eye image component 122R and a left-eye image component 122L, are continuously represented in a stripe shape on a reverse surface (i.e., a focal plane) of the lenticular plate 120. In front of the lenticular plate 120, the right-eye image component 122R and the left-eye image component 122L can be imaged by the right and the left eyes, respectively, via a certain gap therebetween. By viewing the separate right and left image components by the right and the left eyes in this manner, a three-dimensional image (i.e., a stereoscopic image) can be perceived.
By utilizing this principle, Japanese Laid-Open Publication No. 3-65943, for example, discloses a liquid crystal stereoscopic display device in which a three-dimensional dimensional image can be formed by disposing the lenticular plate 120 on a front panel 131 of a liquid crystal display 130 and by alternately inputting the right-eye image component 122R and the left-eye image component 122L to the liquid crystal display 130 every other vertical line of the display 130, as shown in FIG. 13.
In such a stereoscopic display device utilizing the lenticular plate 120, light-blocking portions called a black matrix 133 exist between adjacent pixel openings 132 of the liquid crystal display 130, as shown in FIG. 14. Assuming that a pixel pitch of the liquid crystal display 130 in the horizontal direction and a distance between two adjacent pixels are denoted by L and M, respectively, and that the distance between the eyes of a human viewer is 65 mm, a movement range R of the human eyes within which a stereoscopic image can be perceived is limited to the range defined by the following equation in which an image 132i of the pixel opening 132 is formed with respect to each of the right and the left eyes.
R=65xc3x97M/L
However, in such a stereoscopic display device, if the head or the eyes of the viewer move to exceed the range in which the above equation is satisfied, an image 133i of the black matrix 133 is imaged by the eyes, so that a three-dimensional image cannot be perceived.
Japanese Laid-Open Publication No. 5-346563 discloses a material for an optical modulator using side-chain type polymer liquid crystal molecules containing a photochromic compound as a substituent in a side chain. For example, the photochromic compound may be expressed by the following Formula 1: 
Japanese Laid-Open Publication No. 7-36008 discloses an optical modulator using the side-chain type polymer liquid crystal molecules. In the material for an optical modulator and the optical modulator described in these publications, since the structure of the photochromic compound changes upon the irradiation of light, the orientations of the side-chain type polymer liquid crystal molecules themselves are changed. Because of the change in orientations of the liquid crystal molecules, the light transmitted through the liquid crystal layer is changed, i.e., the absorption spectrum thereof is changed. In other words, information about the light irradiated onto the optical modulator is converted into information about the change in absorption spectrum.
Japanese Laid-Open Publication No. 6-289374 discloses the technologies for locally changing the orientation directions of a liquid crystal layer by using an alignment layer having a photo-orientable polymer network (PPN) and by changing the orientation directions of the polymers upon the irradiation of polarized light.
However, in the case of using such an alignment film having a PPN, a liquid crystal cell is required to be formed on a pair of transparent substrates such as glass substrates so as to attain a sufficient retardation for the alignment film as a phase sheet for stereoscopic display. Thus, a problem is caused in that the production yield is considerably decreased in such a case.
The phase sheet of this invention includes a first region and a second region which have respectively different slow axis directions or fast axis directions. A polymer constituting the sheet contains a photoisomeric molecule.
In one embodiment of the invention, the slow axis directions or the fast axis directions of the first and the second regions are different from each other by about 90 degrees.
In another embodiment of the invention, the polymer is a polymer liquid crystal molecule.
In still another embodiment of the invention, the polymer liquid crystal molecule is a main-chain type polymer liquid crystal molecule.
In still another embodiment of the invention, the polymer liquid crystal molecule is a side-chain type polymer liquid crystal molecule.
In still another embodiment of the invention, an photoisomeric functional group of the photoisomeric molecule is bonded to the polymer.
In still another embodiment of the invention, the polymer contains a polymerizable resin.
In still another embodiment of the invention, a polymerizable functional group of the polymerizable resin is bonded to the polymer.
In still another embodiment of the invention, the polymerizable resin is a compound having a polymerizable liquid crystal structure.
In still another embodiment of the invention, the polymerizable functional group is a photopolymerizable functional group.
In still another embodiment of the invention, the polymerizable functional group is a thermopolymerizable functional group.
In still another embodiment of the invention, the polymer chain has uniaxial properties.
The method of this invention, for fabricating a phase sheet including a first region and a second region which have respectively different slow axis directions or fast axis directions, includes the steps of: forming a pretreatment sheet containing a photoisomeric molecule; and forming the first region and the second region which have respectively different slow axis directions or fast axis directions by irradiating light having an irradiation intensity distribution onto the pretreatment sheet.
In one embodiment of the invention, the method further includes a step of uniaxially orienting the pretreatment sheet.
The stereoscopic display device of this invention, includes a liquid crystal material interposed between a pair of substrates facing each other and a phase sheet, having a first region and a second region which have respectively different slow axis directions or fast axis directions, on at least one of the substrates. The first region and the second region are adjacent to each other, and arranged in a uniform pattern having a symmetry.
In one embodiment of the invention, the phase sheet is provided on a surface of at least one of the pair of substrates, the surface being opposite to a surface thereof facing the liquid crystal material.
The stereoscopic display device of this invention separates a right-eye image component and a left-eye image component from each other by two types of phase difference regions having respectively different slow axis directions or fast axis directions. A liquid crystal material is interposed between a pair of substrates facing each other, and at least one of the substrates includes the two types of phase difference regions having respectively different slow axis directions or fast axis directions.
Hereinafter, the functions or the effects to be attained by the present invention will be described.
In the phase sheet of the present invention, the polymer constituting of the sheet contains an photoisomeric molecule. Thus, in the case of irradiating light onto such a phase sheet with a predetermined pattern, the slow axis directions or the fast axis directions may be different from each other between the phase difference regions, i.e., regions which have been irradiated with light and regions which have not been irradiated with light.
Furthermore, by arranging the phase difference regions (i.e., the first regions and the second regions) formed upon the irradiation of light having such an irradiation intensity distribution so as to respectively correspond to the right-eye pixels and the left-eye pixels, the polarization direction of the light outgoing from the right-eye pixels may be different from that of the light outgoing from the left-eye pixels.
Moreover, the polymer chain constituting of the phase sheet of the present invention preferably has uniaxial properties, and thus may align the orientations of the photoisomeric molecule with a uniaxial direction. As a result, the photoisomeric molecules in the phase sheet may be oriented with a high density.
In the stereoscopic display device of the present invention, the slow axis direction or the fast axis direction of the regions disposed for the right-eye pixels is different from the counterpart of the regions for the left-eye pixels. Thus, by appropriately setting the directions of the polarization axes of the spectacles worn by a viewer for the right eye and the left eye, respectively, the image component from the right-eye pixels may be viewed only by the right eye and the image component from the left-eye pixels may be viewed only by the left eye.
In the stereoscopic display device of the present invention, at least one of the substrates used includes two types of phase difference regions having respectively different slow axis directions or fast axis directions. As a result, before light is transmitted through an isotropic layer such as a glass substrate, the vibration direction of polarized light outgoing from the right-eye pixels may be different from that of polarized light outgoing from the left-eye pixels.
Thus, the invention described herein makes possible the advantage of providing a phase sheet allowing for the perception of a three-dimensional image (i.e., a stereoscopic image) irrespective of a viewing position, a method for fabricating the same, and a stereoscopic display device using the same.
This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.